Field of the Invention
The present invention relates to a power supply apparatus, a printing apparatus, and a control method, and particularly to a power supply apparatus, a printing apparatus, for example, that uses the power supply apparatus, for printing an image on a print medium using an inkjet printhead, and a control method.
Description of the Related Art
For example, a large-format printer apparatus that prints on a large size print medium such as A0 or B0 requires large power for its operation. Thus, in such an apparatus, a current resonance (LLC method) switching power source that can obtain high voltage conversion efficiency at the time of large power supply is widely used. Japanese Patent No. 5179893 discloses an arrangement that includes a burst mode based on this current resonance switching power source. In addition, Japanese Patent No. 5179893 discloses an arrangement that further shortens the soft start time at the start of oscillation in the burst mode than that in a normal activation and performs a burst operation based on a secondary side voltage and further evaluating a feedback signal from the secondary side by using two thresholds.
A predetermined amount of self-consumption occurs during the oscillation period regardless of amount of the load in the current resonance switching power source. Hence, in the current resonance switching power source, a burst operation is excited first, and then the time ratio of the oscillation operation period to a burst period is made small in order to lower the ratio of self-consumption power amount to a load power amount and improve the efficiency when the load is light. Note that in the same manner as in the normal activation, in the start of oscillation during the burst operation, a soft start operation is effective in suppressing element stress and overshooting. The soft start operation in the current resonance switching power source mentioned here is, in particular, an operation that gradually decreases the frequency after starting the oscillation from a high frequency.
In Japanese Patent No. 5179893, the aforementioned time ratio is made smaller by shortening the soft start time in the burst mode than that in the normal activation. In addition, in Japanese Patent No. 5179893, stabilization of secondary side outputs in the burst mode is obtained by controlling the start and stop of oscillation in the burst mode based on the secondary side voltage. Furthermore, in Japanese Patent No. 5179893, a burst period that leads to improvement of efficiency is ensured by evaluating the feedback signal from the secondary side by two thresholds so that a secondary side voltage fluctuation falls within a predetermined value.
The arrangement of Japanese Patent No. 5179893 ensures the burst period while causing the secondary side voltage fluctuation to fall within the predetermined value by evaluating the feedback signal from the secondary side by using two thresholds and evaluates the feedback signal after the error amplifier which is generally designed to have a high gain. That is, each threshold and a voltage amplified several ten to several hundred times by the error amplifier are compared to determine the burst period. Hence, the secondary side voltage fluctuation width falls within a comparatively small range as a result. As a result of the voltage fluctuation width falling within a small range, the oscillation operation count per unit time has a tendency to increase.
As examined above, in the aforementioned conventional technique, the oscillation operation count for the burst period tends to increase, and it may be difficult to implement reduction of power consumption.